This invention relates to removal of ions from water and particularly to cannister systems for removing cations and anions in the rinse water of a plating system.
The need for cleaning water after its use in rinsing parts in plating operations has become of increasing importance. Removal of various materials, particularly metal ions, allows reuse of the rinse water, reducing water and sewer costs. Cleaner rinse water results in improved quality of the plated parts, and eliminates metal hydroxide sludges from waste treatment systems. Valuable metals may also be recovered as a by-product of water-cleaning systems.
One prior art system, disclosed in European Pat. No. 63,236, includes a stack of vessels filled with ion exchange resins through which water to be purified is pumped. Each vessel includes porous end plates through which water passes in an axial direction, except that the bottom vessel is a radial-flow electrolytic cell as well as having a central feedthrough tube for directing water to the second vessel in the stack. The stack of vessels are held between end plates of a frame which pressure-load seals between each vessel to prevent leakage of water as it is pumped through the system.
The multiple-vessel system of the above-mentioned patent has certain desirable features--such as allowing different types of ions to be trapped separately by the use of different resins in selected vessels. Also, when one or more vessels, e.g. vessels near the bottom of the stack, become fully loaded with ions, the stack may be disassembled and vessels with fresh resin added to (the top) of the stack. However, this system has clear disadvantages, such as requiring a large, sturdy frame to pressure load the seals between vessels. A different frame is necessary for each stack of different size--i.e., stacks containing different numbers of vessels or vessels of different heights--and a different frame may be required to hold the vessels during regeneration of their resin. Drainage of water from the system prior to its disassembly also appears cumbersome and time-consuming, even if gravity drainage from vessel to vessel is aided by drainage around seals after release of pressure loading.
Accordingly, it is an object of the invention to provide an improved system for removing ions from water.
It is an object of the invention to provide a system for removing ions from water which is of simple, low cost construction.
It is an object of the invention to provide a system for removing ions from water which includes identical interchangeable cannisters which may be easily interconnected in vertical stacks of differing heights, or in horizontal stacks, and without seals between endwalls of adjacent cannisters.
It is an object of the invention to provide a multi-cannister system for removing ions from water which includes a simple method of determining resin loading in each cannister.
It is an object of the invention to provide a system for removing ions from water which includes cannisters whose contents may be quickly and easily regenerated.